[Alvin]

If that didn't echo what I said... Flame travel higher with ethanol.. check Flame travel highest around lamba .82-.86 or Equivalence ratio 1.1x-1.2 check

 

[BBA]

Sorry Alvin, the answer to my question was alcohol, and nitromethane have a slower burn rate than gasoline. But, you are right, it has a faster flame propagation rate. It still requires more timing advance to build max pressure at TDC.


This article has some Top Fuel detail in it:

Nitromethane also has a high temperature of vaporization, meaning that it will absorb substantial engine heat as it vaporizes, providing an invaluable cooling mechanism. The laminar flame speed and combustion temperature are higher than gasoline at 0.5 m/s and 2400 °C respectively. Power output can be increased by using very rich air fuel mixtures. This is also something that helps prevent pre-ignition, something that is usually a problem when using nitromethane.
Due to the relatively slow burn rate of nitromethane, very rich fuel mixtures are often not fully ignited and some remaining nitromethane can escape from the exhaust pipe and ignite on contact with atmospheric oxygen, burning with a characteristic yellow flame. Additionally, after sufficient fuel has been combusted to consume all available oxygen, nitromethane can combust in the absence of atmospheric oxygen, producing hydrogen, which can often be seen burning from the exhaust pipes at night as a bright white flame. In a typical run the engine can consume as much as 103 litres (22.75 gallons) of fuel during warmup, burnout, staging, and the quarter-mile run.

 

[Alvin]

It does not have a slow burn rate. It's one of the only fuels to be classified as a explosive

 

[BBA]

Happy reading!

http://www.fisita.com/students/congress/sc06papers/f2006sc40.pdf

Nice reading, thanks for the link. Still no answer to my question, the article only compares Ethanol to Heptane to ISO-Octane, it does not compare flame burn rate vs fuel types, completely ignoring gasoline. Instead the test only compares flame propagation rate changes for each of those above listed three fuel types at different mixtures. The simple result: Fuels burn faster initially then slow down over time from ignition with rich mixtures, and fuel burns slow initially and increase burn speed over time from ignition with lean mixtures.

I wonder why no one has any articles comparing the burn rate of differnt fuel types? I think there is some missing information that might show a disadvantage of the politically motivated fuel strategy we are being pushed into.

 

[Alvin]

Isooctane is gasoline. Gas is made up of all kinds of things with isooctane being the primary indgredent

 

[BBA]

Isooctane is gasoline. Gas is made up of all kinds of things with isooctane being the primary indgredent

Gasoline starts from fuel distilled from crude oil, processed to remove some harmful chemicals inherent in the fuel, mixed with other chemicals (including ISO-Octane and a slew of others) etc... to produce the final product commonly referred to as 'Gasoline'.

I guess there is no standard for what exactly Gasoline is...

 

[Billyman]

I wonder why no one has any articles comparing the burn rate of differnt fuel types?

Because the burn rate of fuel(s) is only a repetitive constant when they are ignited under the same conditions. When it comes to engines the burn rate--aka flame travel speed--its different from one configuration to another. As an engine builder, I do many different things and use different parts to increase or decrease the flame speed to fit a specific application.

The information you seek is in the articles but it's not in open defined and/or specified paragraphs. The burn rates are byproducts of the experiments and is why there's nothing in stone.

 

[lt1z]

^^^
best info in this thread

 

[Alvin]

And thats why I said laminar flame travel doesn't mean much to a engine. Whats going on is far from laminar, nor is it consistent as RPM and cylinder pressure (torque) changes.